The researchers looked at more than 7,300 seniors in France with no history of heart disease, stroke or dementia at the start of the study period. Participants were assessed again two, four and seven years later.

Initially, about 30 percent of the women and 15 percent of the men had high levels of depression symptoms. At each follow-up visit, about 40 percent of those with high levels of depression symptoms had recovered, while the same percentage had new depression symptoms, the study authors said.

At all assessments during the study, less than 10 percent of participants were taking antidepressant medications, according to the report published online recently in the Journal of the American Geriatrics Society.

Study participants who had high levels of depression symptoms at any visit had an increased risk of heart disease or stroke over 10 years. But risk rose with depression duration -- from 15 percent if depression symptoms were evident at just one visit to 75 percent if apparent at all four visits, the investigators found.

The findings suggest that depression could be a risk factor for heart disease or stroke. But because this was an observational study, the findings cannot prove a cause-and-effect relationship.

However, based on the findings, study author Dr. Renaud Pequignot, of INSERM in Paris, and colleagues suggested in a journal news release that doctors should closely monitor adults aged 65 and older for symptoms of depression.